Using Ronaldo? Even their higher-ups didn't want him to be at Bayern in the recent transfer window lol.
They can't do anything now because indeed the best way is to change their scheme in the match because regretting not bringing a Striker on the market a while ago is now in vain.
FC Bayern officials took a clear stance against a Cristiano Ronaldo transfer early on. That makes a transfer in the winter transfer window very unlikely. In addition to that, CR7 is not a good fit for Bayern - his attitude doesn't fit to the Bayern MiaSanMia style in which all is about the team and not single players.
And not only that, of course CR7's salary would be a huge issue. He's getting older and his performances get weaker. How do you want to explain it to the rest of the team that he would be the one and only star of the team? Not only when it comes to publicity, but also the salary? Highly unlikely, if you ask me.
FC Bayern has never been a club that spends exorbitant sums on individual players. And fortunately, that will not change in near future.
Therefore, bringing Ronaldo to the Allianz Arena is clearly impossible for now because Bayern's philosophy is very different from Ronaldo's playing style.
We know that some of the officials there didn't want to bring him in transfers last season and now it will be the same because they realize that bringing in Ronaldo could be a blunder for themselves.